The present invention relates generally to an anti-skid brake control system for an automotive vehicle. Specifically, the invention relates to a fail-safe arrangement in an anti-skid brake control system adapted to monitor each of the segments in the control system in order to stop skid control when a fault in one of the segments is detected.
As is well known, it is better not to lock the wheels of a vehicle during braking. Particularly, in order to shorten braking distance to stop the vehicle effectively, wheel-to-road friction .lambda. must be maintained within a given slip-ratio range. In practice, it is considered that the shortest braking distance can be obtained when the slip ratio .lambda. is about 15% vis-a-vis the vehicle speed. In order to keep the slip ratio within the desired range, it is necessary to control application and release of fluid pressure in the actuating cylinders of a hydraulic brake system.
On the other hand, if the anti-skid control system fails the vehicle wheels may lock and significantly degrade the braking distance or the brakes may remain in the released position in spite of the brake pedal being depressed. This can cause serious danger for the vehicle passengers as well as the driver.
Therefore, a fail-safe arrangement for permitting adequate performance of the braking operation even when the anti-skid control system fails would be very desirable.